Hi Florin, I think Dawid might help you. I am pulling him into the discussion.
Best, Andrey > On 12 Dec 2018, at 16:24, Spico Florin <spicoflo...@gmail.com> wrote: > > Hello! > I'm using the same questions as in this stackoverflow post > https://stackoverflow.com/questions/50356981/apache-flink-cep-how-to-detect-if-event-did-not-occur-within-x-seconds?rq=1 > > <https://stackoverflow.com/questions/50356981/apache-flink-cep-how-to-detect-if-event-did-not-occur-within-x-seconds?rq=1>, > due to fact that I need the same functionality. > > My use case is to detect when an device is disconnected from a server (for > example). > From SNMP I'm sending the data to Kafka then to Flink CEP and check whether > I have the established connection within X seconds. > If the window of X seconds timedout, then I can consider that the device is > disconnected. > The issue is that, when the device is disconnected, SNMP does't send anymore > data about that port that was used. Thus no event is sent to CEP. Only when > the device is connected again then, the disconnected event is triggered. > > The same functionality was requested in this post too: > https://stackoverflow.com/questions/51399973/flink-time-window-based-on-event-time-output-nothing > > <https://stackoverflow.com/questions/51399973/flink-time-window-based-on-event-time-output-nothing>. > > I checked the status of the jira ticket regarding this feature: > > https://issues.apache.org/jira/browse/FLINK-7384 > <https://issues.apache.org/jira/browse/FLINK-7384> > > but unfortunately, is still open. > > In the official documentation, > https://ci.apache.org/projects/flink/flink-docs-stable/dev/event_time.html > <https://ci.apache.org/projects/flink/flink-docs-stable/dev/event_time.html>, > in the paragraph related with Idling sources, somehow the situation described > resembles what we need: > "Currently, with pure event time watermarks generators, watermarks can not > progress if there are no elements to be processed. That means in case of gap > in the > incoming data, event time will not progress and for example the window > operator will not be triggered and thus existing windows will not be able to > produce any output data. > To circumvent this one can use periodic watermark assigners that don’t only > assign based on element timestamps. An example solution could be > an assigner that switches to using current processing time as the time basis > after not observing new events for a while." > > Unfortunately, no example of how the mentioned assigner looks like. A full > example will help us to check whether the mentioned solution works or not. > > Therefore, can you please share your thoughts about this feature? > Is feasible? If yes,please provide the Flink version that solve it and the > example. > Is still a limitation and there is no plan to solve it in near future? > > I look forward for your answers. > > Best regards, > Florin > >
